Method for producing a grid structure, an optical element, an evanescence field sensor plate, microtitre plate and an optical communication engineering coupler as well as a device for monitoring a wavelength

Abstract

A coupling grating formed as a line grating with a grating period between 100 nm and 2500 nm, a substrate ( 1 ) is covered with a photoresist layer ( 10 ) and exposed for instance at the Lithrow angle (Θ L ) or at 0° to a mercury-vapour lamp ( 11 ) via a folding mirror ( 13, 13 ′) through a phase mask ( 14 ) in the near field of which the photoresist layer is arranged, then structured by reactive ion etching and provided with a transparent layer by reactive DC magnetron sputtering, particularly pulsed DC sputtering or AC-superimposed DC sputtering. The phase mask ( 14 ) is structured in advance with the laser two-beam interference method. The process is particularly suited for the production of optical elements, particularly evane-scent field sensor plates and optical couplers for communications technology which can be employed in particular as filters for wavelength multiplexing in fibre-optic networks.

1. Evanescent field sensor plate with a platelike substrate with, on a surface portion, a plurality of continuous coupling gratings each formed as a line grating with a grating period between 150 nm and 2000 nm, the coupling gratings being parallel to each other and extending over at least 0.5 cm, and the platelike substrate bears a transparent layer with a refractive index different from that of the substrate, wherein a coupling angle (θ) at which a light beam directed through the substrate to the coupling grating is coupled with the transparent layer with maximum coupling efficiency changes by at most 0.05°/cm along the line grating and the absolute value of deviation of the coupling angle (θ) from a required value on the evanescent field sensor plate does not exceed 0.5°. 
     
     
       2. Evanescent field sensor plate according to  claim 1 , wherein an extension of the coupling grating along the line grating is at least 1 cm. 
     
     
       3. Evanescent field sensor plate according to  claim 1 , wherein the surface area of the coupling grating is at least 10 cm 2 . 
     
     
       4. Evanescent field sensor plate according to  claim 1 , wherein the coupling angle (θ) changes by at most 0.05°/cm along the line. 
     
     
       5. Evanescent field sensor plate according to  claim 1 , wherein the absolute value of deviation of the coupling angle (θ) from its mean value on the evanescent field sensor plate does not exceed 0.3°, and preferably does not exceed 0.15°. 
     
     
       6. Evanescent field sensor plate according to  claim 1 , wherein the refractive index of the transparent layer is between 1.65 and 2.80. 
     
     
       7. Evanescent field sensor plate according to  claim 1 , wherein the transparent layer consists of Ta 2 O 5 , Nb 2 O 5 , TiO 2 , ZrO 2 , Al 2 O 3 , SiO 2 —TiO 2 , HfO 2 , Y 2 O 3 , SiO x N y , Si 3 N 4 , HfO x N y , TiO x N y , MgF 2  or CaF 2 . 
     
     
       8. Evanescent field sensor plate according to  claim 1 , wherein the thickness of the transparent layer is between 50 nm and 200 nm. 
     
     
       9. Evanescent field sensor plate according to  claim 1 , wherein a groove-to-land ratio of the at least one coupling grating is between 0.3:1 and 3:1, preferably between 1.7:1 and 1.5:1. 
     
     
       10. Evanescent field sensor plate according to  claim 1 , wherein a grating depth of at least one coupling grating is between 5 nm and 75 nm. 
     
     
       11. Evanescent field sensor plate according  claim 1 , wherein an at least one coupling grating covers only part of the surface of the evanescent field sensor plate while the remaining part remains free. 
     
     
       12. Evanescent field sensor plate according to  claim 1 , further comprising; at least one coupling grating formed as a strip extending in parallel to the lines, essentially over the entire width or length of the evanescent field sensor plate. 
     
     
       13. Evanescent field sensor plate according to  claim 1 , wherein several coupling gratings in the form of strips are arranged at a distance parallel to each other. 
     
     
       14. Microtitre plate with an evanescent field sensor plate according to  claim 1  as well as with an added honeycomb-shaped top part which laterally defines each of a plurality of cavities arranged in a regular array, the bottom of each of the cavities formed by the evanescent field sensor plate. 
     
     
       15. Optical coupler for communications technology with a platelike substrate with, on a surface portion, a plurality of continuous coupling gratings each formed as a line grating with a grating period between 150 nm and 2000 nm, the coupling gratings being parallel to each other and extending over at least 0.5 cm and the platelike substrate bears a transparent layer with a refractive index different from that of the substrate, wherein a coupling angle (θ), at which a light beam directed through the substrate to the coupling grating is coupled to the transparent layer with maximum efficiency, has an absolute value of deviation from a required value on the coupling grating, the deviation does not exceed 0.5°. 
     
     
       16. Coupler according to  claim 15 , wherein an extension of the coupling grating along the line grating is at least 1 cm. 
     
     
       17. Coupler according to  claim 15 , wherein a surface area of the coupling grating is at least 10 cm 2 . 
     
     
       18. Coupler according to  claim 15 , wherein the coupling angle (θ) changes by at most 0.1°/cm along the line of the coupling grating. 
     
     
       19. Coupler according to  claim 18 , wherein the coupling angle (θ) changes by at most 0.05°/cm along the line. 
     
     
       20. Coupler according to  claim 15 , wherein the absolute value of deviation of the coupling angle (θ) from its mean value on the surface portion does not exceed 0.3°, and preferably does not exceed 0.15°. 
     
     
       21. Coupler according to claim to  claim 15 , wherein the refractive index of the transparent layer is between 1.65 and 2.80. 
     
     
       22. Coupler according to  claim 15 , wherein the transparent layer consists of Ta 2 O 5 , Nb 2 O 5 , TiO 2 , ZrO 2 , Al 2 O 3 , SiO 2 —TiO 2 , HfO 2 , Y 2 O 3 , SiO x N y , Si 3 N 4 , HfO x N y , AlO x N y , MgF 2  or CaF 2 . 
     
     
       23. Coupler according to  claim 15 , wherein a thickness of the transparent layer is between 50 nm and 200 nm. 
     
     
       24. Coupler according to  claim 15 , wherein a groove-to-land ratio of the at least one coupling grating is between 0.3:1 and 3:1, preferably between 1.7:1 and 1.5:1. 
     
     
       25. Coupler according to  claim 15 , wherein a grating depth of the at least one coupling grating is between 5 nm and 75 nm. 
     
     
       26. Coupler according to  claim 15 , wherein a surface portion bears at least two regular coupling gratings with different grating periods. 
     
     
       27. Coupler according to  claim 15 , wherein a surface portion bears at least one irregular coupling grating in which the distance between neighboring grating lines is not constant. 
     
     
       28. Coupler according to  claim 27 , wherein in the irregular coupling grating the grating period changes linearly in a direction normal to the lines only. 
     
     
       29. Device for monitoring a wavelength with a coupler according to  claim 27  as well as with a detector assembly arranged directly beneath the coupler, the device having at least two photodetectors arranged consecutively normal to the lines. 
     
     
       30. Device according to  claim 29 , wherein the detector arrangement is displaceable in a direction normal to the lines relative to the coupler.